In a host of applications, flow direction measurements are necessary. For example, aboard modern fighter aircraft, it is necessary to measure angle of attack that conventionally involves the utilization of a vane which is responsive to air streams across its surface for sensing angle of attack. Similar vane instruments are employed in other airflow measurements such as wind direction and hydraulic flow.
Although such devices often operate satisfactorily, their mechanical nature involves inherent disadvantages. One of these disadvantages is the inherent problem of unreliability in adverse environments. Minor deterioration in mechanical components will adversely affect the data being generated by vane instruments. Further, such vane instruments are exceedingly sensitive to turbulence or extraneous air streams in the vicinity where they are mounted so as to sense flow components that are not of interest. An additional disadvantage is the lag time for responding to quick changes in flow direction.